Composite conductor



COMPOSITE CONDUCTOR Filed Dec. 9. 1926 zZO Patented June 9, 1931 UNITED STATES WILLIAM G. KNOX, OF MANHASSET, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NE'W YORK COMPOSITE CONDUCTOR A plication filed December 9, 1926.

This invention relates to the construction of signaling conductors and more particularly to the construction of such conductors continuously loaded with magnetic material.

The loading of signaling conductors with 16 its form in applying it to a conductor. It

is therefore, best to perform the heat-treating operation upon the loaded conductor, but even then certain structural precautions must be taken for best results.

A structural precaution provided in accordance with this invention resides in a thin layer of chromium between the conductor and the loading material. Preferably the chromium is in the form of a coat,- ing which is adherent either to the conductor or to the loading material.

Another feature of the invention relates to the method of preparing such a loaded conductor which comprises, first plating with chromium either the individual strands from which the conductor is to be prepared, the solid or stranded conductor itself, or the unapplied loading material, and then applying the loading material over the conductor. Electroplating is a preferred process for obtaining an adherent coating of chromium.

A more detailed description of the invention follows and is illustrated in the accompanying drawings.

Fig. 1 illustrates a continuous process for electroplating a single strand.

Fig. 2 shows a section of a loaded conductor with a portion cut way to illustrate details of construction.

Fig. 3 is a cross-sectional View of the conductor of Fig. 2.

Until comparatively recently iron has been considered to be the only material suitable for the continuous loading of sig- Serial No. 153,678.

naling conductors. It has been discovered, however, that material, in general, more suitable than iron may be produced in the form of alloys. When nickel and iron are alloyed in proper proportions and the alloy is given a proper heat treatment, a material having properties peculiarly suited for continuous loading of signaling conductors is obtained. One alloy which. is peculiarly desirable because of its high permeability has a composition comprising 78 nickel and 21 /270 iron. An other magnetic alloy which exhibits very great constancy of permeability under the conditions encountered in signaling circuits comprises nickel, 30% iron and 25% cobalt. However, in order to bring out the desirable qualities in these alloys they must be properly heat treated. For a detailed description of these loading materials, see an article P in the Journal of the Franklin Institute, volume 195, No. 5, for May 1923, by Messrs. Arnold and Elmen entitled Permalloy, an Alloy of Remarkable Magnetic Properties and the United States Patent No. 1,715,646 issued to G. W. Elmen June 4, 1929.

When it is attempted to employ these materials either in the form of tape or wire for continuous loading of a conductor, difiiculties are encountered. Desired qualities which are attainable by proper heat treatment prior to the placing of the material uponthe conductor are deleteriously affected by the mechanical strains incident to the application process; hence, the finished conductor is heat treated. A suitable heat treatment for obtaining the desired properties of. both the nickel-iron and nickel-ironcobalt alloys comprises heating the alloy to approximately 900 C. after it has been applied to the copper conductor. During such process, a condition arises which prevents desired magnetic or electrical properties of the loading material, as for example, high attainable permeability, from being attained.

The present invention is one of a series of inventions which have been made with the object of avoiding this condition.

The preferred process of continuously electroplating chromium on a metallic strand or conductor is shown in Fig. 1, in which the strand or conductor 10, to be plated, is supplied from a rotable reel 11. A break lever 12 engaging the reel and the tension spring 13 regulates the rotation of the reel 11. The strand 10 enters a hot alkali bath 14, contained in a metallic tank 15, through which it is guided by a plurality of iron pulleys or rollers 16. The hot alkali bath consists of approximately one pound of caustic soda to eachgallon of water, and forms a cleansing solution to remove foreign substances from the metallic strand 10. The strand is drawn through a water bath 17 to wash the strand after leaving the alkali bath and a wiper 14 surrounds the strand 10 adjacent the end of the alkali bath treatment to prevent an excess of alkali solution being carried to the water bath. The rollers 18 engaging the strand 10 during the washing operation are preferably of brass or bronze to prevent injurious oxides from being formed at these points and applied to the conductor in contact with the rollers.

The strand is then drawn through the acid dip bath 19 to remove scale coating prior to the electroplating operation. Ihis bath comprises from one to two pounds of concentrated hydrochloric acid to each gallon of water but may be a concentrated hydrochloric acid bath and is preferably contained in a glass or porcelain tank20. The rollers 21 for this bath are preferably of rubber which is substantially unaffected by the acid. A wiperl22, also of rubber, removes excessive acid solution fromthe strand 10 after it leaves the acid bath. The next bath 23 is the same as the bath 17, namely, a clear water bath, to rinse the strand after the acid bath. A suitable tap 24 may be positioned over the strand to supply a constant flow of water to 'wash the strand.

The strand then enters chromium-plating bath 25 which is contained in a lead-lined tank 26. The formula for the plating bath is substantially the same as disclosed in an article entitled Principles and operating conditions of chromium-plating by H. E. Haring, in the Chemical and Metallurgical Engineer, volume 32, August 25, 1925. This bath consists of chromic acid C10,, 250 grams; chromium sulphate Cr (SO 3 grams; and chromium carbonate Cr O (COQ 7 grams; added to sufficient water to make a liter of solution. This bath is maintained at a temperature of from 36 to 38 C. by a heater enclosed in an 'oil filled glass tube 27, or any other type of immersion heater. The heater is connected to a source of current such asbattery 28 and the current supply controlled by a variable resistance 29. A copper orbronze roller 30 is supported adjacent the plating bath to form the cathode contact for the strand 10. The cathode contact roller 30 and the lead lining of the tank 26 which acts as the anode of the bath are connected to a source of voltage 31 through an ammeter 32 and a variable resistance 33. By this arrangement the current density in the solution is maintained at the required values to form a smooth bright chromium coating on the strand 10 which is the cathode of the electrolytic bath by virtue of its contact engagement with the roller 30. The values of the current; density which have been found desirable are approximately 125 to 145 amperes per square foot of anode surface. Suitable porcelain or glass rollers 34, guide the strand 10 through the electrolytic bath. After the chromium-plated strand leaves the bath a wiper 35 removesthe excess solu- 1 tion from the strand to prevent the pollution of the washing bath 36 through which the plated strand is passed guided by brass rollers 37. Auxiliary washing streams of water are supplied from taps 38 arranged over the strand andflow into the final washing tank. A drying wiper 86 surrounds the strand 10 after leaving the washing bath 36 and the strand is wound on a take-up reel-39. This arrangement forms a continuous process for treating and electroplating conducting strands to form a coating of pure chromium on the surface thereof.

Referring toiFigs. 2 and 3, a plurality of flatcondrictingstrands 40 which have been electroplated with chromium, are wrapped helically on a central conducting core 41, and a magnetic tape 42 is applied over the conducting strands, to form a composite conductor which may be heat treated to 'improve the desired properties of the tape 42.

While the invention has been described with respect to the continuous process of treating and electroplating a single strand, it is apparent that a large number of strands may be carried through the process simultaneously. Furthermore, the chromium-plating can be applied to a solid conductor such as the core 41, and the magnetic tape v42 applied directly to the chromiumiplating on the solid conductor.

A possible explanation for the deleterious effects produced by the heat treating process is that unless precautions are taken adhesion takes place between the copper? "120 conductor and the loading material. In the process of heating the loaded. conductor at about 900 C. the copper expands considerably more than the surrounding loading material and if there is not sullicient slack in the loading material very close contact is established between the two, either in the furnace or just after the conductor enters the cooling chamber. Contraction of the loading layer is rapid in the latter stage of the heat treatment due to the cooling medium coming in contact directly with this layer. Due to the increased molecular activity at the elevated temperature of 900 C. diffusion between the two metals appears to be established and welding or adhesion takes place over portions at least of the contact surfaces. Upon cooling of the copper conductor the latter tends to draw away from the magnetic loading material and since this material partially adheres to the copper, stresses are set up which are great enough to deleteriously affect the properties of the loading material.

WVhile the invention has been particularly described with reference to loaded signaling conductors it may be employed in other types of composite strands which are subj ected to high temperature conditions and in which contact between the individual strands durin the heating or subsequent cooling gives rise to deleterious effects.

hat is claimed is:

1. A signaling conductor comprising a plurality of component strands in close contact, and a thin layer of chromium on the contacting surface of at least one of said component strands, said layer being effective in preventing adhesion of said one strand to another of said strands during a heat treatment at temperatures of 700 C. or higher.

2. A signaling conductor comprising a plurality of component strands in close contact, and a coating of chromium electroplated on the contacting surface of at least one of said component strands, said layer being effective in preventing adhesion of said one strand to another of said strands during a heat treatment at a temperature of approximately 7 00 C. or higher.

3. A composite signaling conductor comprising a central strand, a magnetic strand wound thereon, said magnetic strand being subject to adhesion to said central strand during heat treatment, and a thin layer of chromium between said strands, said layer being adherent to one of said strands.

4. A composite signaling conductor comprising a central strand, a magnetic strand wound thereon, said magnetic strand being subject to adhesion to said central strand during heat treatment, and an electrolytic deposit of chromium on the surface of one of said strands in contact with the other strand.

5. A loaded conductor comprising a central core, a plurality of strands wrapped about said core, a magnetic material wound around said strands, said magnetic material being subject to adhesion to said strands during heat treatment, and a thin layer of chromium electrolytically deposited on said strands. Y

6. A loaded signaling conductor comprising a conducting strand, a magnetic loading material wrapped about said strand, said loading material requiring heat treatment to develop high permeability therein and the permeability being sensitive to strain, and a coating of chromium separating the loading material from said conducting strand.

7. A loaded signaling conductor comprising a central conductor, a plurality of conducting strands spirally applied to said conduct-or, a layer of magnetic loading material surrounding said strands, said signaling conductor being subjected to heat treatment to increase the permeability of said loading material, and an electroplated coating of chromium between said loading material and conducting strands.

8. The method of producing a composite strand free from adhesion between the coinponent strands during heat treatment, which consists in forming a chromium coating on one of the component strands, and superimposing another strand on said coated strand.

9. The method of producing a composite strand free from adhesion between the component strands during heat treatment, which consists in electrolytically depositing chromium on one of the component strands, and superimposing another strand on said deposited strand.

10. The method of loading a signaling conductor with magnetic material which requires heat treatment to improve its magnetic properties, which comprises forming a layer of chromium on the conductor, and wrapping the magnetic material in contact with said chromium layer.

11. The method of loading a signaling conductor with magnetic material which requires heat treatment to increase the electrical characteristics of the magnetic material, which consists in electrolytically depositing chromium on a conducting strand,

wrapping said strand spirally on a central strand, and wrapping a layer of magnetic loading material about said deposited strand.

12. The method of producing a stranded. signaling conductor free from adhesion between the several strands of said conductor, which consists in coating chromium on the separate strands, winding said strands ina layer on a core, and wrapping a layer of magnetic material on said coated layer.

13. The method ofproducing a stranded signaling conductor free, from adhesion between the several strands of said conductor, which consists in electroplating chromium on the separate strands, winding said strands in a layer on a core, and wrapping a layer of magnetic material on said electroplated layer.

14. A signaling conductor comprising an electrically conducting strand, a mass of loading material in close proximity to the surface of said conducting strand, at least one of said elements having a coating of chromium whereby the structure may be sub jected to heat treatments at temperatures of the order of 700 C. and higher Without adliesion between said elements.

15. The method of producing a loaded signaling conductor which comprises a con ductor element and an element of magnetic material which comprises coating one of said elements with chromium, assembling said elements to form a structure in which the magnetic element lies closely adjacent the surface of the conducting element and heated during the assembly of the structure at a temperature of the order of 900 C. to improve the magnetic characteristics of the assembled structure whereby the chromium coating prevents adhesion between said elements.

In witness whereof, I hereunto subscribe my name this 8th day of December A. D.,

WILLIAM G. KNOX. 

